1. Field of the Invention
The present invention relates to a piezoelectric resonance component and, more particularly, to a piezoelectric resonance component used for high frequency apparatuses and other electronic devices.
2. Description of the Related Art
There is a known piezoelectric resonance component of this type having a structure as shown in FIG. 6 (for example, see Japanese examined utility model publication No. S58-34819). This piezoelectric resonance component 15 includes a piezoelectric resonator 2 which is supported by a ring terminal 8, a dot terminal 9 and a ground terminal 12 such that the piezoelectric resonance component 15 can vibrate in an outer case 1. As shown in FIG. 7, the piezoelectric resonator 2 includes a ring-shaped peripheral electrode 4 and a dot-shaped center electrode 5 on one side of a piezoelectric substrate 3 and a ground electrode 6 on the other side of the substrate 3. The center electrode 5 is located inside the peripheral electrode 4.
As shown in FIG. 8, the ring terminal 8 and the dot terminal 9 are disposed such that they face an inner bottom surface of the outer case 1. A lead portion 8a of the ring terminal 8 is provided along one inner wall 1a of the outer case 1. Each of a pair of arm portions 8b vertically extending to the lead portion 8a is bent to provide a triangular protrusion 8c. A lead portion 9a of the dot terminal 9 is provided along an inner wall 1b of the outer case 1 facing the inner wall 1a. A protrusion 9c is provided on a terminal portion 9b which is extended from the lead portion 9a to be located between a pair of arm portions 8a of the ring terminal 8.
The piezoelectric resonator 2 is disposed above the ring terminal 8 and the dot terminal 9 with a sheet-shaped anisotropic conductor 7 interposed therebetween such that the side having the peripheral electrode 4 and the center electrode 5 faces downward. The anisotropic conductor 7 has conductivity in the direction of the thickness thereof but has no conductivity in the direction of the plane thereof. Therefore, the peripheral electrode 4 of the piezoelectric resonator 2 is in electrical conduction to the protrusions 8c of the ring terminal 8 through the anisotropic conductor 7. Similarly, the center electrode 5 of the piezoelectric resonator 2 is in electrical conduction to the protrusion 9c of the dot terminal 9 through the anisotropic conductor 7.
The conventional piezoelectric resonance component 15 has a structure in which the anisotropic conductor 7 has substantially the same size as the piezoelectric resonator 2 and the positions of the center of the anisotropic conductor 7 and the protrusion 9c of the dot terminal 9 substantially coincide with each other. As a result, when the piezoelectric resonator 2 is inclined toward the dot terminal 9 such that an edge of the anisotropic conductor 7 is in contact with the dot terminal 9 as indicated by the alternate long and short dash lines in FIG. 6, the dot terminal 9 is put in conduction to the peripheral electrode 4 of the piezoelectric resonator 2 through the anisotropic conductor 7 and the peripheral electrode 4 is put in conduction to the protrusions 8c of the ring terminal 8 through the anisotropic conductor 7. That is, there has been a problem in that the dot terminal 9 and the ring terminal 8 are short-circuited which results in the piezoelectric resonator not being able to function.
In order to solve this problem, a piezoelectric resonance component has been proposed wherein, as shown in FIG. 9, the anisotropic conductor 7 is replaced with an anisotropic conductor 14 which has an anisotropic conductive region 7a only at a portion thereof where electrical contact is required and has insulating properties in the remaining portions thereof and wherein the anisotropic conductor 14 is provided between the piezoelectric resonator 2 and the dot terminal 9 and between the piezoelectric resonator 2 and the ring terminal 8.
However, in the anisotropic conductor 14 which has conductivity only at a portion thereof which must have conductivity, a problem has arisen in that the material cost has been high because of its special structure. Further, a positional shift of the anisotropic conductor 14 in the outer case 1 could result in non-conductivity between the center electrode 5 of the piezoelectric resonator 2 and the protrusion 9c of the dot terminal 9 and non-conductivity between the peripheral electrode 4 of the piezoelectric resonator 2 and the protrusions 8c of the ring terminal 8. This has resulted in a need for forming the anisotropic conductor 14 to have substantially the same dimensions as those of the resonator-containing portion of the outer case 1 to suppress the positional shift of the anisotropic conductor 14 in the outer case 1. However, when the anisotropic conductor 14 is constructed to have substantially the same dimensions as those of the resonator-containing portion of the outer case 1, it becomes difficult to insert the anisotropic conductor 14 from an opening of the outer case 1 using an automatic assembling apparatus. Further, both of the piezoelectric resonance component using the anisotropic conductor 7 in FIG. 6 and the piezoelectric resonance component using the anisotropic conductor 14 in FIG. 9 have had a problem in that the vibration of the piezoelectric resonator 6 is significantly damped by the anisotropic conductors 7 and 14 which are in contact with the entire surface of the piezoelectric resonator 2.